If the FDA accepts the Circulatory System Devices Advisory Panel's recommendation, the Navistar ThermoCool RF it would be the first of its kind approved as second-line therapy in symptomatic paroxysmal atrial fibrillation. The FDA is not obliged to follow advisory panel recommendations but it usually does.

The device, already FDA-approved for use in type I atrial flutter, is marketed in 39 other countries for atrial fibrillation. "I think this will add a very important tool to the electrophysiologist's toolkit," said panel member David Slotwiner, M.D. Ph.D., an electrophysiologist at Long Island Jewish Medical Center in New Hyde Park, N.Y.

The device is manufactured by Biosense Webster, which is owned by Johnson & Johnson. The panel, chaired by Jeffrey Borer, M.D., of Weill Cornell Medical College, heard data from an industry-sponsored study showing that patients receiving cardiac ablation with the ThermoCool device were less likely to have atrial fibrillation nine months later than those given standard medical therapy.

"The process of atrial fibrillation ablation is really exploding out there regardless of whether it's approved, simply because it works," Hugh Calkins, M.D., of John Hopkins, an electrophysiologist who consults for Johnson & Johnson, told the advisers.

After delivery to the heart by catheter, the RF device pulses energy through the catheter's tip. The catheter operator targets and burns an area of the atrium, creating a lesion that essentially traps the potential energy that is thought to cause the irregular heartbeat in paroxysmal atrial fibrillation patients.

For the FDA-monitored, multicenter, unblinded study, 167 patients with symptomatic paroxysmal atrial fibrillation who were refractory or intolerant to antiarrhythmic drug therapy and who had at least three episode of atrial fibrillation in the previous six months, were randomized two to one to ablation or standard medical therapy.

The primary effectiveness endpoint was "chronic success," which was defined as a patient being free from symptomatic atrial fibrillation based on electrocardiographic data and having no change in their drug treatment at nine months.

Treatment for 53 out of 89 patients (60%) in the ThermoCool group was considered a success, while nine out of 56 (16%) patients with medical therapy had successful treatment.

"It looks like this therapy is three times as effective as giving drugs," said panel member Judah Weinberger, M.D., of Columbia University.

Although the event rate was lower in the ThermoCool group, the confidence interval's upper bound was slightly higher than specified in the trial protocol.

About 10% of ThermoCool patients had a serious adverse event, such as hospitalization, within seven days from treatment. About 14% control patients had a serious adverse event.

At 90 days, the ThermoCool group had far fewer adverse events than the control group (18% versus 35%).

At the daylong advisory committee meeting, the panel expressed concern about the small size of the study and the fact that the foreign sites reported much better results that those in the U.S..

The company attributed the discrepancy partly to the product's longer availability in Europe, giving operators time to become more skilled at ablations.

But the advisors said they felt comfortable enough with the domestic data to recommend FDA approval.

In the study, those performing ablations relied on use of Biosense's own 3D Carto mapping system, which allows the operator to get a clear picture of the atrium to ablate more accurately. The panel recommended the FDA approve the catheter only in conjunction with the company's mapping system.

"To perform that without the 3D mapping system, especially for less experienced operators, may be a challenge," said Dr. Slotwiner. "For less experienced operators, I'm not sure the same results could be replicated that we saw in the trial," he said.

Other panel members pointed out that not all electrophysiologists need the 3D assistance, and requiring its use would be a costly burden for many centers.

A spokesman for Johnson & Johnson declined to comment on the cost of the mapping system.

The panel also voted to recommend a physician training program for operators and establish a registry that will, in part, look at how the experience of an operator affects outcomes of ablation.

Reviewed by Zalman S. Agus, MD Emeritus Professor University of Pennsylvania School of Medicine